#define _CRT_SECURE_NO_WARNINGS 1
#include <stdio.h>

int main() {
	double sum = 0;
	int i;
	int n = 1;
	for (i = 1; i <= 100; i++) {
		sum = sum + 1.0 / i *n;
		n = -n;
	}
	printf("%lf", sum);
}